JPH0723587A - Pole detecting circuit and driver for three-phase brushless synchronous motor employing it - Google Patents

Abstract

PURPOSE:To prevent step out by comparing the output from a differential amplifier, for detecting the differential voltage between the terminals of a winding from a counter electromotive force having phase shifted through a primary low-pass filter, with a zero volt potential. CONSTITUTION:A voltage Vab between terminals is fed through a primary low-pass filter (LF) 11a where noise components are removed from counter electromotive forces Va, Vb and the phase of main component is shifted by about 60 deg.. Main components of the counter electromotive forces Va, Vb subjected to phase shift are then fed to a differential amplifier 12a and the differential voltage is outputted as a voltage waveform Da between terminals. The waveform Da is fed to a comparator 13a where it is compared with a zero volt potential. The comparator 13a outputs a pulse of 180 deg. width having phase lag of about 60 deg. behind the zero-cross point of the voltage waveform Vab between terminals. In other words, a pole position detecting circuit 10a generates a pole position signal Pa. Similarly, detecting circuits 10b, 10c generate pole position signals Pb, Pc. The pole position signals Pa, Pb, Pc have 120 deg. phase shift.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic pole detection circuit for generating a magnetic pole position signal equivalent to a magnetic pole sensor for detecting the rotational position of a magnetic pole on the basis of a counter electromotive voltage generated in an armature winding, and the magnetic pole. The present invention relates to a drive device for driving a three-phase brushless synchronous motor using a detection circuit.

[0002]

2. Description of the Related Art As a magnetic pole sensor for detecting a rotational position of a three-phase brushless synchronous motor, a system using a counter electromotive voltage generated at a terminal of an armature winding has been actively researched in recent years and various systems have been developed. Have been proposed.

A drive device for a general three-phase brushless synchronous motor, which utilizes a back electromotive force generated at the terminals of the armature winding as a magnetic pole sensor, has a structure as shown in FIG.

A three-phase bridge circuit 1 composed of _six semiconductor switching elements Q ₁ to Q ₆ is supplied with power from a DC power supply 2. For example, in the case of a 120-degree conduction angle conduction control system, a three-phase brushless synchronization is used. 12 for each phase of motor 3
A rectangular wave with a conduction angle of 0 degree is applied at a predetermined timing.

[0005] In the circuit pole detection circuit 4 to enter the terminal voltage of the three-phase brushless synchronous motor 3 of the armature winding _{V a, V b, V c} , to generate a magnetic pole detection signal for commutation, more specifically Specifically, the configuration is as shown in FIG.

That is, in FIG. 6, the armature winding 3-1.
The counter electromotive voltage generated at each terminal of the armature winding 3-1 is detected with reference to the virtual neutral point of the three resistors 5 star-connected to each terminal of The phase is shifted by 90 degrees by the primary low-pass filter 6 having a sufficiently low cutoff frequency, and the corresponding comparator 7 is provided with a position signal for commutation, that is, a magnetic pole detection signal.

Based on the magnetic pole detection signal thus obtained, the control circuit 8 in FIG. 5 generates gate signals for the semiconductor switching elements Q ₁ to Q ₆ in the three-phase bridge circuit 1 at a predetermined timing, Control is performed so that a rectangular wave having a conduction angle of 120 degrees is applied from the three-phase bridge circuit 1 to each phase of the three-phase brushless synchronous motor 3.

[0008]

However, the configuration of the magnetic pole detection circuit 4 as shown in FIG. 6 has a drawback that a problem occurs at the time of heavy load.

That is, the terminal voltage when the three-phase brushless synchronous motor 3 is unloaded has a waveform as shown by the solid line in FIG. 7 (A), and the terminal voltage V ₁₀ when unloaded is the primary low-pass. When it is passed through the filter 6, a waveform V ₁₁ with the phase shifted by 90 degrees as shown by the dotted line in FIG. 7A is generated. When this signal waveform V ₁₁ is used as a commutation signal, the three-phase brushless synchronous motor 3 can obtain relatively stable rotation.

However, the three-phase brushless synchronous motor 3
The terminal voltage when the load is heavy has a waveform in which the spike voltage is superimposed as shown by the solid line in FIG. 7B, and the terminal voltage V ₁₂ at the time of the heavy load is the primary low-pass filter. 6 shows a waveform V ₁₃ where the phase advances from 90 degrees as shown by the dotted line in FIG. 7B, and when the advance angle exceeds 30 degrees, the three-phase brushless synchronous motor 3 causes step out, A situation occurs in which it stops.

The present invention has been made in view of the above points, and the inventors have experimentally detected a magnetic pole position signal based on an interphase voltage rather than a phase voltage, and generate a commutation signal from the detected signal. It was found that driving a phase brushless synchronous motor is less susceptible to spike voltage under heavy load.Therefore, such a structure is adopted, and the magnetic pole sensor is not used and step out occurs and the motor stops. It is an object of the present invention to provide a magnetic pole detection circuit that does not exist and a drive device for a three-phase brushless synchronous motor using the magnetic pole detection circuit.

[0012]

In order to achieve the above object, the magnetic pole detection circuit of the present invention and a drive unit for a three-phase brushless synchronous motor using the magnetic pole detection circuit are rectangular waves with a conduction angle of 120 degrees for each phase. In a drive device of a three-phase brushless synchronous motor having a star-shaped armature winding to be driven, the phase is shifted to a delayed phase near 60 degrees at a predetermined frequency based on the counter electromotive voltage generated in each phase. 3 sets of primary low-pass filters to be operated, and the differential voltage between the terminals of the armature winding is detected from the back electromotive force whose phase is shifted by the primary low-pass filter 3
The magnetic pole detection circuit includes a pair of differential amplifiers and three pairs of comparators that compare the output of the differential amplifier and the zero volt potential.

In the drive device for the three-phase brushless synchronous motor, the magnetic pole detection circuit described above, a control circuit that generates a commutation signal based on the magnetic pole position signal output from the magnetic pole detection circuit, and the control circuit generate the commutation signal. And a three-phase bridge circuit that outputs a rectangular wave with a conduction angle of 120 degrees to each of the above phases by a commutation signal to drive the three-phase brushless synchronous motor.

[0014]

Since the spike voltage of the inter-terminal voltage is superimposed 60 degrees before the zero cross point and immediately after the zero cross point, the spike voltage is less likely to be affected by the heavy load.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention. In the figure, numerals 1, 3, 8 correspond to those in FIG.

Reference numeral 11 is a first-order low-pass filter, 12 is a differential amplifier, and 13 is a comparator. For example, the inter-terminal voltage (back electromotive force) V _ab of the three-phase brushless synchronous motor 3 is input to the first-order low-pass filter 11 and the differential amplifier 12 at the uppermost stage, and the cutoff frequency is sufficiently low. The PWM conduction waveform is smoothed by the next low-pass filter 11, the noise component is removed, and only the main component of the counter electromotive voltage whose phase is shifted by about 60 degrees is extracted and input to the differential amplifier 12. The difference component is appropriately amplified by the differential amplifier 12, and the terminal voltage waveform D _a output from the differential amplifier 12 becomes the terminal voltage (back electromotive force) waveform V _ab . On the other hand, the phase is delayed by about 60 degrees as shown in FIG.

The voltage waveform D _a between terminals and the zero volt potential from the differential amplifier 12 are input to the comparator 13. When the inter-terminal voltage waveform D _a is larger than the zero volt potential, the comparator 13 outputs the H level, so that the magnetic pole position signal P _a shown in FIG. . As is apparent from FIG. 2, the magnetic pole position signal P _a is a pulse whose width is delayed by about 60 degrees from the zero cross point of the inter-terminal voltage (back electromotive voltage) waveform V _ab and is 180 degrees.

Similarly, the middle-stage comparator produces a magnetic pole position signal P _b delayed by about 60 degrees from the zero crossing point of the terminal voltage (back electromotive force) waveform V _bc , and the lowest-stage comparator. Generates a magnetic pole position signal P _c delayed by about 60 degrees from the zero crossing point of the inter-terminal voltage (back electromotive force) waveform V _ca.

In this way, three sets of comparators 13 are generated.
Magnetic pole position signal P_a, P_b, P _cBased on the control circuit
8 is a semiconductor in the three-phase bridge circuit 1 at a predetermined timing
Switching element Q₁Through Q₆Control to turn on
U

FIG. 4 shows a specific circuit of an embodiment of the magnetic pole detection circuit. In the figure, 10a to 10c are magnetic pole position detection circuits, 11a to 11c are primary low-pass filters, 12a to 12c are differential amplifiers, and 13a to 13c are comparators.

First-order low-pass filters 11a to 11c
The terminal voltages of the three-phase brushless synchronous motor 3, that is, the back electromotive voltages V _a , V _b , and V _c generated in each phase are input to the respective terminals as shown in FIG.

Explaining, for example, the magnetic pole position detection circuit 10a, the inter-terminal voltage V _ab is input to the primary low pass filter 11a, and the counter electromotive voltage V _a input by the primary low pass filter 11a. , V _b noise components are removed (for example, smoothing of PWM energization waveform)
At the same time, the phase of its main component is shifted by about 60 degrees. The time constant of the primary low-pass filter 11a is determined by the desired rotation speed of the three-phase brushless synchronous motor 3 and the alternating frequency determined by the number of magnetic poles of the rotor magnet. Actually, as will be described later, from the experimental results, the above-mentioned time constant gives a good result in which the phase shift is about 65 degrees.

The main components of the counter electromotive voltages V _a and V _b whose phases are thus shifted are input to the differential amplifier 12a,
The difference voltage is output as the terminal voltage waveform D _a . The inter-terminal voltage waveform D _a is input to the non-inverting input terminal of the comparator 13a and compared with the zero volt potential input to the inverting input terminal of the comparator 13a.

As described with reference to FIG. 2, from the comparator 13a, a width delayed by about 60 degrees (experimentally about 65 degrees is good) from the zero cross point of the terminal voltage waveform V _ab is equivalent to 180 degrees. The pulse is output. That is, the magnetic pole position detection circuit 10a generates the magnetic pole position signal P _a .

Similarly, the magnetic pole position detection circuits 10b, 10
Magnetic pole position signals P _b and P _c having similar conditions are generated from _c . The magnetic pole position signals P _a , P _b , and P _c have a phase shift of 120 degrees.

Generally, in the case of a drive device for a three-phase brushless synchronous motor using a Hall IC or the like as a rotor position sensor, the position of the Hall IC is aligned with the counter electromotive voltage between the terminals of the three-phase brushless synchronous motor. Is said to be the norm.

However, in the case of the present invention, when the counter electromotive voltage of the energized armature winding 3-1 is detected as a position signal, the PWM chopper voltage is superimposed on the counter electromotive voltage of the armature winding 3-1. And the above-mentioned first-order low-pass filter 11
a works to smooth it and at the same time shifts the phase. Therefore, in the first-order low-pass filter 11a, the shift width is about 60 degrees (experimentally about 65 degrees).
It is set to a time constant of degree. Other magnetic pole position detection circuit 10
The same applies to the first-order low-pass filters b and 10c.

FIG. 3 shows an embodiment of the armature under heavy load.
A waveform explanatory diagram is shown, and V_a, V _bIs the terminal voltage waveform,
V_abRepresents the voltage waveform between terminals. Terminal voltage waveform
V_a, V_bThen, as explained in FIG. 7 of the conventional example, 120 degrees
Spike voltage is generated when width energization is off.

On the other hand, in the inter-terminal voltage waveform V _ab , the spike voltage is superimposed as in the case of the terminal voltage waveforms V _a and V _b , but the timing of occurrence is the above-mentioned terminal voltage waveform V _a , Different from the case of V _b . The spike voltage on the terminal voltage waveforms V _a and V _b is 30 from the zero cross point.
The spike voltages A and C on the voltage waveform V _ab between the terminals are 60 degrees before the zero cross point,
The spike voltages B and D are superimposed on the positions immediately after the zero crossing points. From this, it is easily understood that the inter-terminal voltage waveform V _ab is less likely to be affected by the phase of the waveform after the primary low-pass filter 11a. That is, in the case of FIG. 6 of the conventional example in which the terminal voltage is viewed from the virtual neutral point [waveform at heavy load is FIG. 7 (B)], the spike voltage is generated 30 degrees before the zero cross point. When passing through the next low-pass filter 6, the spike voltage is superimposed on the back electromotive force, and the phase delay is advanced beyond 90 degrees. The heavier the load, the stronger the tendency.

However, in the present invention, as described above, the spike voltage A is 60 degrees before the zero cross point, so that the effect of the spike voltage A is less than that of the conventional example in terms of time.
Further, since the spike voltage B is generated after the zero cross point, the influence is further eliminated.

It has been confirmed in an actual experimental example that the load is about three times the rated value and the progress is about 10 degrees. Therefore, by using the magnetic pole detection circuit described above, the three-phase brushless synchronous motor 3 can be stably rotated without a magnetic pole sensor for detecting the position of the rotor.

[0032]

As described above, according to the present invention, it is possible to generate a magnetic pole position signal without a magnetic pole sensor, and by using the magnetic pole detection circuit, step out does not occur and a predetermined rotation is performed. The three-phase brushless synchronous motor can be stably rotated up to several widths.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a waveform explanatory diagram of magnetic pole position signal generation.

FIG. 3 is a waveform explanatory diagram of an embodiment of an armature under heavy load.

FIG. 4 is a specific circuit of an embodiment of a magnetic pole detection circuit.

FIG. 5 is a configuration diagram of a driving device of a three-phase brushless synchronous motor.

FIG. 6 is a configuration diagram of a conventional magnetic pole detection circuit.

FIG. 7 is a waveform explanatory diagram of a conventional magnetic pole detection circuit.

[Explanation of symbols]

 1 three-phase bridge circuit 2 DC power supply 3 three-phase brushless synchronous motor 3-1 armature winding 4 magnetic pole detection circuit 8 control circuit 10a, 10b, 10c magnetic pole position detection circuit 11 primary low-pass filter 12 differential amplifier 13 comparator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Satoshi Kawai 39 Toba, Chiyo-ji, Konan-cho, Osato-gun, Saitama Prefecture Inside Zekcel Gangnam Plant (72) Inventor Kyo Hagiwara 1-20-12 Minamihashimoto, Sagamihara-shi, Kanagawa Prefecture No. 703 (72) Inventor Yasuo Ono 2-4-12 Namiki, Sagamihara-shi, Kanagawa (72) Inventor Kiyo Nara 1-4-15 Kanumadai, Sagamihara-shi, Kanagawa

Claims (2)

[Claims] 1. A drive device for a three-phase brushless synchronous motor, wherein each phase is provided with a star-shaped armature winding that is driven by a rectangular wave with a conduction angle of 120 degrees, and a counter electromotive voltage generated in each phase is used as a basis. Between the three sets of primary low-pass filters that shift the phase to a lag phase near 60 degrees at a predetermined frequency, and the back electromotive force whose phase is shifted by the primary low-pass filter, between the terminals of the armature winding. A magnetic pole detection circuit comprising: three sets of differential amplifiers for detecting a difference voltage; and three sets of comparators for comparing the output of the differential amplifier and a zero volt potential. 2. A drive device for a three-phase brushless synchronous motor, wherein each phase is provided with a star-shaped armature winding driven by a rectangular wave having a conduction angle of 120 degrees, and a counter electromotive voltage generated in each phase is used as a basis. Between three sets of primary low-pass filters that shift the phase to a lag phase near 60 degrees at a predetermined frequency, and the back electromotive force whose phase is shifted by the primary low-pass filter between each terminal of the armature winding. A magnetic pole detection circuit including three sets of differential amplifiers for detecting a differential voltage and three sets of comparators for comparing the output of the differential amplifier with a zero volt potential, and a magnetic pole position output by the magnetic pole detection circuit. 1 for each phase by a control circuit that generates a commutation signal based on the signal and a commutation signal that is generated by the control circuit.
A drive device for a three-phase brushless synchronous motor, comprising: a three-phase bridge circuit that outputs a rectangular wave with a conduction angle of 20 degrees and drives the three-phase brushless synchronous motor.